The Influences of different cathode materials on Tris-(8-Hydroxyquinoline)- Aluminum Doped with CsNO$_{3}$ in Organic Light emitting Devices

This paper presents the investigations of interfacial interactions and electron-injection mechanisms between cesium nitrate (CsNO$_{3})$ and different cathode materials. By using ultraviolet and x-ray photoemission spectroscopy, the properties of electronic structures and the interfacial chemistry are studied. According to our results, there exists a phenomenon of electron exchange at the interface results in changes of Aluminum 2s core level binding energy by 1 eV when aluminum was deposited on CsNO$_{3.}$ This means electrons transfer from cathode materials to the surface of CsNO$_{3}$, forming a strong dipolar field at the interface and reduction of the electron injection barrier. But, in contract, there exists nearly no reaction between CsNO$_{3}$ and silver cathode. The evidences show that CsNO$_{3}$ is more effective only with aluminum cathode due to a reaction between Aluminum, Cesium and Nitrogen atoms.